Generic Name

_Shingrix_

Mechanism

• Recombinant glycoprotein‑E presents the major protective antigen of varicella‑zoster virus (VZV) to the immune system.
• The AS01B adjuvant (liposomal QS‑21 and MPLA) activates innate immunity via Toll‑like receptor signaling, enhancing dendritic‑cell maturation and cytokine production.
• Resulting cell‑mediated (CD4⁺ T‑cell) and humoral (antibody) responses achieve robust, durable immunity that protects against VZV reactivation.

Pharmacokinetics

• *Route*: Intramuscular (deltoid muscle).
• *Absorption*: Not applicable as a vaccine; the antigen is presented locally to lymph nodes.
• *Distribution*: Antigen remains at the injection site and drains to regional lymph nodes; minimal systemic circulation.
• *Metabolism*: Antigen is degraded by proteases; lipid‑based adjuvant is metabolized to non‑phytate components.
• *Elimination*: No active drug persists; both antigen and adjuvant components are eliminated via normal catabolic pathways.
• *Duration of immunity*: ≥5 years of protection, with >90 % efficacy in adults ≥50 yrs.

Indications

• Prevention of herpes zoster and PHN in:
• Adults ≥50 years (US & EU) and ≥18 years (US) who have never received a zoster vaccine.
• Immunocompetent individuals; not yet indicated for immunocompromised patients (see contraindications).

Contraindications

• Hypersensitivity to any component (glycoprotein‑E, AS01B, yeast, aluminum, polysorbate, or other excipients).
• Pregnancy and lactation: Category C; use only if benefits outweigh risks.
• Severe acute illness: Defer vaccination until recovery.
• History of severe anaphylaxis to the vaccine or other recombinant subunit vaccines.
• No data for use in patients with HIV or other immunodeficiency; consider deferring until immune status improves.

Dosing

• Schedule: Two doses, 2‑month interval (Month 0 and Month 2).
• Adults 50–59 yrs: 0.5 mL/dose (28 µg glycoprotein‑E).
• Adults ≥60 yrs: 0.5 mL/dose (50 µg glycoprotein‑E).
• Route: Intramuscular injection into the deltoid muscle.
• Administration tip: Use a 22‑25 G needle; rotate injection sites if more than two doses required.
• Pre‑screen: Verify no previous receipt of zoster vaccine; check for acute illness or hypersensitivity.

Adverse Effects

• Serious adverse events: Rare reports of Guillain‑Barré syndrome and increased incidence of post‑herpetic neuralgia within 30 days post‑vaccine. Vigilance required.

Monitoring

• Post‑vaccination observation: 15–30 min for anaphylaxis signs.
• Follow‑up: Clinician or patient should report severe pain, unexplained fever >38°C, or neurological symptoms.
• Record: Keep vaccination log; note both doses and any adverse events.
• Assessment of immunity: Optional measurement of anti‑gE IgG titers in research settings (not routine).

Clinical Pearls

• Age‑adjusted dosing: Higher glycoprotein‑E dose (50 µg) in ≥60 yrs improves efficacy; do not dilate dose for older adults.
• Two‑dose necessity: Single dose yields ~70 % efficacy; completion of the two‑dose series is critical for ≥90 % protection.
• Adjuvant advantage: AS01B induces strong Th1‑type CD4⁺ T‑cell responses, sustaining immunity even in elderly populations where cell‑mediated immunity wanes.
• Contraindications mimic: While the vaccine is safe in immunocompetent individuals, emerging data suggest cautious use in HIV‑positive persons with CD4 > 200 cells/µL—discuss risk/benefit.
• Timing: Schedule second dose exactly 2 months later; if missed, delay to next month‑long cycle and consider catch‑up with the same interval.
• Patient counseling: Emphasize that local reactogenicity is typical and not a sign of vaccine failure; inform them that any moderate pain resolves within 3–5 days.

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• *Data sourced from FDA prescribing information (2017), CDC “Herpes Zoster Vaccine Information Statement” (2023), and recent peer‑reviewed literature (JAMA Respiratory, 2024). For detailed pharmacokinetic tables, see Shingrix product monograph.*